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Thread: Wiring an Electric Cooling Fan - Holley EFI

  1. #11

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    Danny, why do you prefer to use ground triggers instead of +12V?

  2. #12
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    Quote Originally Posted by 3pedals View Post
    Danny, why do you prefer to use ground triggers instead of +12V?
    Because if there's ever a wiring problem, such as a chaffed/shorted wire, it doesn't damage the circuit.
    A short circuit on a ground triggered Output, will activate the electric fans, not render them inoperable.
    Also, if the Output fails, it's much easier to jump the circuit with a jumper wire to ground, than find +12V.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #13
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    Danny, I'm not really sure about diodes. If I want to put one on a negative trigger wire coming from the ECU to my fan relay, do I put the Anode side towards the ECU, and the Cathode side towards the relay?
    Richard
    1969 C-10 SWB Step
    355 Small Block
    Stealth Ram, Holley HP EFI
    700R4 Trans, 2500 stall & 3.73 gears

  4. #14
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    Quote Originally Posted by riche View Post
    Danny, I'm not really sure about diodes. If I want to put one on a negative trigger wire coming from the ECU to my fan relay...
    You can simply use a diode protected relay (see center of post #1), and avoid installing a separate diode.

    ...do I put the Anode side towards the ECU, and the Cathode side towards the relay?
    Check the polarity (Link) before permanently installing it in the circuit. A diode only allows current to flow in one direction (Link).
    If the ECU provides +12V power, connect the Anode to the ECU. If the ECU provides Ground, connect the Cathode to the ECU.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #15

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    Does anyone have experience with solid state relays? I have Hella H41773001 relays that I assumed (incorrectly) were interchangeable with standard Bosch relays, since they plug right in, and don't come with a wiring diagram. I have my fans setup with a PWM- signal and the relays are behaving strangely. The fans are on when the key is off, but turn off when I turn the key on. Everything works fine with a standard relay. I also have a +12V triggered circuit that does not work correctly with a solid state relay, but works fine with a standard one.

    I did some Googling and found that these relays don't operate exactly the same as Bosch type mechanical relays, and need to be wired differently. Some even claim the terminals need to be changed, but I can't find a definitive wiring diagram anywhere. Here is a link describing some of the same issues I'm having: Click. Removing the wire suggested in this thread does not seem like it would solve my problem, but I haven't tried it either. Also, this guy suggests running a separate relay to cut power because of the PWM dumping to ground. I'm pulsing the ground, so I'm not sure if this is relevant. Adding another relay is a deal breaker for me and I will just abandon the PWM and use standard relays. I also am not wild about changing the pin locations, since then I can't swap relays in a break-down situation unless I switch all of my relays to solid state. Any input?

  6. #16
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    Quote Originally Posted by racindego View Post
    I have Hella H41773001 relays that I assumed (incorrectly) were interchangeable with standard Bosch relays, since they plug right in, and don't come with a wiring diagram.
    Correct. It has the same relay terminal configuration, but different relay wiring.
    That solid state relay has one +12V supply, one +12V output & two grounds.

    #30 - High Amperage +12V (Battery)
    #87 - Load (Fan, Light, Pump, etc.)
    #86 - Switched Ground (Trigger)

    #85 - High Amperage Ground

    http://hellahd.com/index.php/default/electrics/relays/mini-iso-relays/12v-spst/h41773001-931773987/
    (Hella H41773001 Relay)
    http://hellahd.com/index.php/download_file/-/view/2796/ (Technical Data Sheet PDF)
    http://www.hella.com/ePaper/Elektrik/Relais/englisch/document.pdf (Hella Relay Catalog - Page 10)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #17

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    OK, so removing the +12V key wire should fix my problem on the fans. It must be getting some kind of feedback and messing with the relay operation. On my other relay, since it's wired to be triggered by +12V, I cannot use a solid state relay. That's unfortunate. And I can't rewire to trigger with ground since the HP only allows 2 of each output. I would have liked to use all the same relay wiring so I can swap in case of a failure, but I guess that isn't possible?
    Thanks Danny!

  8. #18
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    Quote Originally Posted by racindego View Post
    I would have liked to use all the same relay wiring so I can swap in case of a failure, but I guess that isn't possible?
    No, that's not possible with a solid state relay and a conventional (mechanical) relay.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  9. #19

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    Both links from post #16 show terminal 85 not connected to anything with a note that says "N.C.".
    I thought this was some type of reference to "Normally Closed" for use in a different application.
    It definitely doesn't show terminal 85 as a ground. What am I missing?

    EDIT: I found the answer on page 10 here, which shows the terminal wiring exactly as you described:
    http://www.hella.com/ePaper/Elektrik/Relais/englisch/document.pdf

    Still not sure what N.C. means on the other diagrams?

  10. #20
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    Quote Originally Posted by racindego View Post
    Still not sure what N.C. means on the other diagrams?
    Ignore the abbreviation; it means No Contacts (or Not Contacted). It's just their way of stating that terminal is permanently grounded.
    It's a normally open solid state relay with no mechanical contacts. Post #16 has all the pertinent relay information you need to wire it.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

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